The present invention relates to inflatable balloons and more particularly to inflatable toroidal-shaped balloon catheters for medical procedures.
Balloon catheters are well known in the art. Such catheters are employed in a variety of medical procedures, including dilation of narrowed blood vessels, placement of stents and other implants, and temporary occlusion of blood vessels, and other vascular uses.
In a typical application, the balloon is advanced to the desired location in the vascular system. The balloon is then pressure-expanded in accordance with a medical procedure. Thereafter, the pressure is removed from the balloon, allowing the balloon to contract and permit removal of the catheter. It is to be appreciated that the balloon is preferably formed of an elastomeric material which is readily pressure-expanded, yet will also readily contract upon removal of the inflation pressure.
Procedures such as these are generally considered minimally invasive, and are often performed in a manner which minimizes disruption to the patient's body. As a result, catheters are often inserted from a location remote from the region to be treated. For example, during angioplasty procedures involving coronary vessels, the balloon catheter is typically inserted into the femoral artery in the groin region of the patient, and then advanced through such vessel into the coronary region of the patient. These catheters typically include some type of radiopaque marker to allow the physician performing the procedure to monitor the progress of the catheter through the body. However, because the balloon portion of the catheter is not visible to the physician, the balloon may be over inflated without the physician's awareness. This is particularly concerning when large diameter balloons are employed in medical procedures because the maximum hoop stress of the inflated balloon material can more easily be exceeded causing the balloon to rupture or burst.
There are two main forms of balloon catheter devices, compliant and non-compliant balloons. Non-compliant balloons employ a relatively strong but generally inelastic material (e.g., polyester) folded into a compact, small diameter cross section. These relatively stiff catheters are used to compact hard deposits in vessels. Due to the need for strength and stiffness, these devices are rated to employ high inflation pressures, usually up to about 8 to 12 atmospheres depending on rated diameter. They tend to be self-limiting as to diameter, thus they will normally distend up to the rated diameter and not distend appreciably beyond this diameter until rupture due to over-pressurization. While the inelastic material of the balloon is generally effective in compacting deposits, it tends to collapse unevenly upon deflation, leaving a flattened, folded balloon substantially larger in cross section than the balloon was prior to inflation. This enlarged, folded balloon may be difficult to remove, especially from small vessels. By contrast, compliant balloons are used to remove soft deposits, such as thrombus, where a soft and tacky material such as a latex provides an effective extraction means. Latex and other highly elastic materials generally will expand continuously upon increased internal pressure until the material bursts. As a result, these catheters are generally rated by volume (e.g., 0.3 cc) in order to properly distend to a desired size. Although relatively weak, these catheters do have the advantage that they tend to readily return to their initial size and dimensions following inflation and subsequent deflation. The weak nature of the elastomer material used in these types of balloon catheters has restricted their use to small diameter balloon applications; typically less than 4 to 5 mm diameter. The stress generated in the inflatable balloon material is defined as hoop stress and is a function of the product of the inflation pressure and the inner diameter of the inflated balloon, divided by the wall thickness of the inflated balloon. Accordingly, the hoop stress increases linearly with increasing balloon diameter. Therefore, there have been efforts to reinforce embolectomy elastic balloon catheters.
Some of the catheter balloons constructed of both elastomeric and non-elastomeric materials have been described previously. As the length of their balloon portion decreases, the length of the movable portion of the outer tubing increases and by proper selection of internal diameters and lengths of the two portions, the shortening of the balloon is offset.
U.S. Pat. No. 5,647,848 teaches a structure formed of helically extending fibers, including bundles of continuous monofilaments, aramide, polyethylene, steel, polyester, glass, carbon, and ceramics. The fibers are positioned in an elastomer such that the fibers lie at an angle which is less than a neutral angle of 54.73 degrees relative to the axis of the balloon when the balloon is unpressurized. With the utilization of rigid fibers the balloon will be non-compliant in its fully inflated state.
Some medical procedures which require the use of a relatively large diameter balloon would greatly benefit from a balloon with a small uniflated diameter that would return to that initial size and dimensions following inflation and subsequent deflation. The means for reinforcing the elastic balloon catheters to date have not addressed both the low profile and high burst pressure requirements for large diameter balloon applications. Accordingly, there is a need in the art for large diameter elastomeric balloons that can maintain a shape profile upon inflation and that can withstand high inflation pressure. In addition, there is a need in the art for a large diameter elastomeric balloon with a relatively short axial length, and a toroidal-shaped inflated balloon that maintains a shape profile upon inflation, can withstand high inflation pressure, and can be made to only partially occlude the vessel upon inflation.
Temporary brachytherapy is a medical application that involves positioning catheters into areas such as the prostate or colon, for the purpose of giving a series of radiation treatments through these catheters. The catheters are easily pulled out after the treatment and no radioactive material is left in the body. A balloon catheter that secures the radioactive material in the center of a vessel would be advantageous in these applications as it would provide for more uniform dosing or treatment of the vessel, tube or orifice with radiation and minimize any excessive dosing to the interior wall of the vessel. There is a need for a balloon catheter that can secure the radioactive element and reach large diameters for applications such as colon temporary brachytherapy.
The use of bioresorbable materials in balloon catheters have been used to seal wounds and to repair vessels. In such applications, a toroidal-shaped bioresorbable balloon would be ideal for sealing the wound in a minimally invasive manner. In addition, a toroidal-shaped balloon can be used in large-neck aneurysms to bridge over the large neck and make a small neck aneurysm, which is then easier to pack in Gugliemi Detachable Coils. Intestinal wall reinforcement is another application for a toroidal-shaped bioresorbable balloon.